The U.N. Security Council, including Russia, agreed on Wednesday to a statement endorsing efforts by Kofi Annan to end the Syrian uprising, providing a rare moment of global unity in the face of the year-long crisis.
The statement, which threatens Syria with unspecified "further steps" if it fails to comply with a six-point peace plan drawn up by Annan, will be formally adopted in New York later in the day, diplomats said.
U.S. Secretary of State Hillary Clinton on Wednesday praised the move as a "positive step".
"To President Assad and his regime we say, along with the rest of the international community: take this path, commit to it, or face increasing pressure and isolation," Clinton told reporters after a meeting with Afghanistan's foreign minister.
Although the original Western-drafted statement had to be diluted at Russia's demand, editing out any specific ultimatums, the fact that all major powers signed up to the proposal represented a blow to President Bashar Assad, who is fighting for his survival.
At least 8,000 people have died in the revolt, according to U.N. figures, with the violence intensifying in recent weeks as pro-government forces bombard rebel towns and villages, looking to sweep their lightly armed opponents out of their strongholds.
U.N. chief Ban Ki-moon said on Wednesday that the crisis was alarming and had "massive repercussions" for the entire world.
"We do not know how events will unfold. But we do know that we all have a responsibility to work for a resolution of this profound and extremely dangerous crisis," Ban said in a speech in the Indonesian capital Jakarta.
Syria lies in a pivotal position at the heart of a web of regional conflicts in the Middle East, comprising a mix of faiths, sects and ethnic groups, and diplomats fear the rebellion is degenerating into a full-blown civil war.
Assad's forces have chalked up a string of gains as they turned their firepower on areas held by rebels, but the fighting shows no sign of abating and analysts expect the insurgents to change their tactics and adopt guerrilla warfare.
Opposition activists said the army used tanks, artillery and anti-aircraft guns on the Damascus suburbs of Harasta and Irbin early Wednesday, which were retaken from rebels two months ago but have seen renewed insurgency in recent days.
Elsewhere, the army fired mortars into the Khalidiya district of Homs, while artillery targeted the rebel town of Rastan, north of Homs city, in central Syria. Video also showed shelling of the ancient Apamea castle at Qalat Mudiq, near Hama.
Reports from Syria cannot be independently verified because officials have barred access to rights groups and journalists.
Russia and China have vetoed two previous U.N. draft resolutions that would have condemned Damascus and have resisted calls from Western and Arab states for Assad to stand down.
But faced by growing global outrage at the bloodshed, the two countries agreed to a so-called "presidential statement", which are generally non-binding documents that nonetheless require unanimous support in the Security Council.
Speaking after the UN agreement was reached, Britain's Foreign Secretary, William Hague, said: “I strongly welcome the Security Council’s full and unanimous support for the work of Kofi Annan as joint UN-Arab League envoy, expressed in today’s Presidential statement.
"I urge the Syrian authorities to take this chance to stop the bloodshed and show their commitment to implementing Kofi Annan’s six point plan, including by immediately pulling back the military from in and around population centers."
Reuters and msnbc.com staff contributed to this report.